Apex domains cannot have CNAME records.
Question and response
Question
dig ar.edu.do. NS
Answer
ar.edu.do. 5 NS customer-ns2.kxe.io.
ar.edu.do. 5 NS customer-ns1.kxe.io.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0